A cooling structure of a multi-cylinder engine is provided, which includes a water jacket formed in a cylinder block to surround cylinder bores of cylinders arranged inline, a spacer, and a coolant inlet. The spacer includes openings at positions corresponding to inter-cylinder-bore portions and a rectifying part extending outwardly on a lower side of the openings. The rectifying part inclines continuously upwardly while extending in one of an exhaust- and intake-side section of the jacket from a first end side to a second end side that is the opposite side from the first end side in a cylinder line-up direction, extending on the second end side from the one of the exhaust- and intake-side sections to the other one of the exhaust- and intake-side sections, and then extending from the second end side to the first end side in the other one of the exhaust- and intake-side sections.

A cooling structure of an engine is provided, which includes a water jacket formed in a cylinder block to surround a cylinder bore of the engine, a spacer having a vertical wall surface and inserted into the water jacket, and a coolant inlet formed in an outer wall of the water jacket, and for circulating to the water jacket coolant introduced from the coolant inlet. The vertical wall surface surrounds the cylinder bore. The spacer includes a guide part provided at a position of a lower end part of the vertical wall surface corresponding to the coolant inlet, and for guiding the coolant introduced from the coolant inlet to flow around the vertical wall surface. The guide part extends outwardly from the lower end part of the vertical wall surface toward the coolant inlet along a bottom wall of the water jacket.

A cooling structure of an engine is provided, which includes a water jacket formed in a cylinder block to surround a cylinder bore of the engine, a spacer having a vertical wall surface and inserted into the water jacket, and a coolant inlet formed in an outer wall of the water jacket, and for circulating to the water jacket coolant introduced from the coolant inlet. The vertical wall surface surrounds the cylinder bore. The spacer includes a guide part provided at a position of a lower end part of the vertical wall surface corresponding to the coolant inlet, and for guiding the coolant introduced from the coolant inlet to flow around the vertical wall surface. The guide part extends outwardly from the lower end part of the vertical wall surface toward the coolant inlet along a bottom wall of the water jacket.

A cooling structure of a multi-cylinder engine is provided, which includes a first water jacket formed in a cylinder block to surround cylinder bores of cylinders arranged inline, a spacer having a vertical wall surface and inserted into the first jacket, and a coolant inlet formed in the first jacket on a first end side in a cylinder line-up direction. The structure circulates coolant introduced from the inlet to the first jacket and a second water jacket formed in a cylinder head coupled to the cylinder block via a gasket. The spacer has a flow dividing rib extending outwardly from the vertical wall surface and for vertically dividing the coolant flow, introduced from the inlet to an intake- or exhaust-side section of the first jacket, toward the second jacket through a communication hole formed in the gasket and toward a discharging section provided to the cylinder block.

A cooling structure of a multi-cylinder engine is provided, which includes a first water jacket formed in a cylinder block to surround cylinder bores of cylinders arranged inline, a spacer having a vertical wall surface and inserted into the first jacket, and a coolant inlet formed in the first jacket on a first end side in a cylinder line-up direction. The structure circulates coolant introduced from the inlet to the first jacket and a second water jacket formed in a cylinder head coupled to the cylinder block via a gasket. The spacer has a flow dividing rib extending outwardly from the vertical wall surface and for vertically dividing the coolant flow, introduced from the inlet to an intake- or exhaust-side section of the first jacket, toward the second jacket through a communication hole formed in the gasket and toward a discharging section provided to the cylinder block.

Systems are provided for a cooling arrangement of an engine. In one example, a system includes a first coolant passage and a second coolant passage arranged in a cylinder bridge between directly adjacent cylinders, wherein the first coolant passage and the second coolant passage are separated from one another.

Systems are provided for a cooling arrangement of an engine. In one example, a system includes a first coolant passage and a second coolant passage arranged in a cylinder bridge between directly adjacent cylinders, wherein the first coolant passage and the second coolant passage are separated from one another.

The present invention is configured such that: a cylinder block includes an introducing portion provided at a first side of a cylinder row, cooling liquid being introduced through the introducing portion to a water jacket, a restrictor portion provided in a vicinity of the introducing portion and configured to restrict the cooling liquid, introduced through the introducing portion, from flowing to an intake-side portion of the water jacket, and a discharging portion provided at a middle portion of the cylinder row at an intake side, the cooling liquid being discharged from the water jacket through the discharging portion; and an exhaust-side portion of the water jacket is formed such that a passage cross-sectional area of a cylinder axis direction upper side of the exhaust-side portion is larger than the passage cross-sectional area of a cylinder axis direction lower side of the exhaust-side portion.

The present invention is configured such that: a cylinder block includes an introducing portion provided at a first side of a cylinder row, cooling liquid being introduced through the introducing portion to a water jacket, a restrictor portion provided in a vicinity of the introducing portion and configured to restrict the cooling liquid, introduced through the introducing portion, from flowing to an intake-side portion of the water jacket, and a discharging portion provided at a middle portion of the cylinder row at an intake side, the cooling liquid being discharged from the water jacket through the discharging portion; and an exhaust-side portion of the water jacket is formed such that a passage cross-sectional area of a cylinder axis direction upper side of the exhaust-side portion is larger than the passage cross-sectional area of a cylinder axis direction lower side of the exhaust-side portion.

A cooling structure of an engine includes a cylinder head and a coolant temperature sensor. The cylinder head gas a first water jacket for cooling a combustion chamber and a second water jacket for cooling an exhaust manifold. The cylinder head includes a joining portion where coolants from the first water jacket and the second water jacket join together. The joining portion has a first coolant passage. A second coolant passage is disposed downstream of the joining portion. The temperature sensing portion is disposed in the second coolant passage. A coolant outlet of the second water jacket is defined in the first coolant passage, and is located at a position on the cylinder head cover attachment surface side in the first coolant passage. The temperature sensing portion is located at a position on the cylinder block attachment surface side in the second coolant passage.